Has a cycling training rulebook for plan updates. The rules are:

Heart rate zone:
  - garmin is the source of truth for HR zones
  - recommend changes to set zones as needed

Core Gear Rules:
- Only one gear ratio per workout.
- Gears can change between workouts within a setup.
- Switching between setups (Setup 1 ↔ Setup 2) only every ≥4 weeks.

Setup Definitions:
- Setup 1 (endurance/cadence bias): 
    - 38×18 (harder)
    - 38×20 (easier)
- Setup 2 (strength/force bias):
  - 38×14 (harder)
  - 38×16 (easier)

Workout-to-Gear Matching:
- Endurance / Z2 → easiest gear in setup.
- Tempo / Sweet Spot → harder gear in setup.
- Climbing / Strength Endurance → hardest manageable gear.
- Cadence / Recovery → easiest gear.

Terrain & Gradient:
- Steep climbs (>10%) → Setup 1 only.
- Flat/rolling → Setup 2 acceptable.
- Avoid spinning >110 rpm or grinding <60 rpm for long periods.

Adaptation:
  - Stay in setup ≥4 weeks; may extend up to 6–8 weeks if progress continues.
  - Switch setups after recovery week.

Fallback Rules:
  - If terrain/weather forces a change, stay in current setup, pick easier gear.
  - Missing a ride does not reset setup timing.

Meta-Rule:
- When creating or updating the plan, rules must always be consulted and applied.